using System.Collections.Concurrent;
using System.Reflection;
using Jint.Collections;
using Jint.Native;
using Jint.Native.Object;
using Jint.Native.Symbol;
using Jint.Runtime.Descriptors;
using Jint.Runtime.Interop.Reflection;

namespace Jint.Runtime.Interop
{
    public sealed class TypeReference : Constructor, IObjectWrapper
    {
        private static readonly JsString _name = new("typereference");
        private static readonly ConcurrentDictionary<Type, MethodDescriptor[]> _constructorCache = new();
        private static readonly ConcurrentDictionary<MemberAccessorKey, ReflectionAccessor> _memberAccessors = new();

        private readonly record struct MemberAccessorKey(Type Type, string PropertyName);

        private TypeReference(Engine engine, Type type)
            : base(engine, engine.Realm, _name)
        {
            ReferenceType = type;

            _prototype = engine.Realm.Intrinsics.Function.PrototypeObject;
            _length = PropertyDescriptor.AllForbiddenDescriptor.NumberZero;

            var proto = new TypeReferencePrototype(engine, this);
            _prototypeDescriptor = new PropertyDescriptor(proto, PropertyFlag.AllForbidden);

            PreventExtensions();
        }

        public Type ReferenceType { get; }

        public static TypeReference CreateTypeReference<T>(Engine engine)
        {
            return CreateTypeReference(engine, typeof(T));
        }

        public static TypeReference CreateTypeReference(Engine engine, Type type)
        {
            var reference = new TypeReference(engine, type);
            engine.RegisterTypeReference(reference);
            return reference;
        }

        protected internal override JsValue Call(JsValue thisObject, JsValue[] arguments)
        {
            // direct calls on a TypeReference constructor object is equivalent to the new operator
            return Construct(arguments, Undefined);
        }

        public override ObjectInstance Construct(JsValue[] arguments, JsValue newTarget)
        {
            static ObjectInstance ObjectCreator(Engine engine, Realm realm, ObjectCreateState state)
            {
                var arguments = state.Arguments;
                var referenceType = state.TypeReference.ReferenceType;

                var fromOptionsCreator = engine.Options.Interop.CreateTypeReferenceObject(engine, referenceType, arguments);
                ObjectInstance? result = null;
                if (fromOptionsCreator is not null)
                {
                    result = TypeConverter.ToObject(realm, FromObject(engine, fromOptionsCreator));
                }
                else if (arguments.Length == 0 && referenceType.IsValueType)
                {
                    var instance = Activator.CreateInstance(referenceType);
                    result = TypeConverter.ToObject(realm, FromObject(engine, instance));
                }
                else
                {
                    var constructors = _constructorCache.GetOrAdd(
                        referenceType,
                        t => MethodDescriptor.Build(t.GetConstructors(BindingFlags.Public | BindingFlags.Instance)));

                    var argumentProvider = new Func<MethodDescriptor, JsValue[]>(method =>
                    {
                        var parameters = method.Parameters;

                        if (parameters.Length == 0)
                        {
                            return arguments;
                        }

                        var newArguments = new JsValue[parameters.Length];
                        var currentParameter = parameters[parameters.Length - 1];
                        var isParamArray = currentParameter.ParameterType.IsArray &&
                                           currentParameter.GetCustomAttribute(typeof(ParamArrayAttribute)) is not null;

                        // last parameter is a ParamArray
                        if (isParamArray && arguments.Length >= parameters.Length - 1)
                        {
                            var currentArgument = JsValue.Undefined;

                            if (arguments.Length > parameters.Length - 1)
                            {
                                currentArgument = arguments[parameters.Length - 1];
                            }

                            // nothing to do, is an array as expected
                            if (currentArgument.IsArray())
                            {
                                return arguments;
                            }

                            Array.Copy(arguments, 0, newArguments, 0, parameters.Length - 1);

                            // the last argument is null or undefined and there are exactly the same arguments and parameters
                            if (currentArgument.IsNullOrUndefined() && parameters.Length == arguments.Length)
                            {
                                // this fix the issue with CLR that receives a null ParamArray instead of an empty one
                                newArguments[parameters.Length - 1] = new JsArray(engine, 0);
                                return newArguments;
                            }

                            // pack the rest of the arguments into an array, as CLR expects
                            var paramArray = new JsValue[Math.Max(0, arguments.Length - (parameters.Length - 1))];
                            if (paramArray.Length > 0)
                            {
                                Array.Copy(arguments, parameters.Length - 1, paramArray, 0, paramArray.Length);
                            }
                            newArguments[parameters.Length - 1] = new JsArray(engine, paramArray);

                            return newArguments;
                        }

                        // TODO: edge case, last parameter is ParamArray with optional parameter before?
                        if (isParamArray && arguments.Length < parameters.Length - 1)
                        {
                            return arguments;
                        }

                        // optional parameters
                        if (parameters.Length > arguments.Length)
                        {
                            // all missing ones must be optional
                            int start = parameters.Length - arguments.Length;
                            for (var i = start; i < parameters.Length; i++)
                            {
                                if (!parameters[i].IsOptional)
                                {
                                    // use original arguments
                                    return arguments;
                                }
                            }

                            Array.Copy(arguments, 0, newArguments, 0, arguments.Length);

                            for (var i = parameters.Length - 1; i >= 0; i--)
                            {
                                currentParameter = parameters[i];

                                if (i >= arguments.Length - 1)
                                {
                                    if (!currentParameter.IsOptional)
                                    {
                                        break;
                                    }

                                    if (arguments.Length - 1 < i || arguments[i].IsUndefined())
                                    {
                                        newArguments[i] = FromObject(engine, currentParameter.DefaultValue);
                                    }
                                }
                            }

                            return newArguments;
                        }

                        return arguments;
                    });

                    foreach (var (method, methodArguments, _) in TypeConverter.FindBestMatch(engine, constructors, argumentProvider))
                    {
                        var retVal = method.Call(engine, null, methodArguments);
                        result = TypeConverter.ToObject(realm, retVal);

                        // todo: cache method info
                        break;
                    }
                }

                if (result is null)
                {
                    ExceptionHelper.ThrowTypeError(realm, $"Could not resolve a constructor for type {referenceType} for given arguments");
                }

                result.SetPrototypeOf(state.TypeReference);

                return result;
            }

            // TODO should inject prototype that reflects TypeReference's target's layout
            var thisArgument = OrdinaryCreateFromConstructor(
                newTarget,
                static intrinsics => intrinsics.Object.PrototypeObject,
                ObjectCreator,
                new ObjectCreateState(this, arguments));

            return thisArgument;
        }

        private readonly record struct ObjectCreateState(TypeReference TypeReference, JsValue[] Arguments);

        public override bool Equals(JsValue? other)
        {
            if (other is TypeReference typeReference)
            {
                return this.ReferenceType == typeReference.ReferenceType;
            }

            return base.Equals(other);
        }

        internal override bool OrdinaryHasInstance(JsValue v)
        {
            if (v is IObjectWrapper wrapper)
            {
                return wrapper.Target.GetType() == ReferenceType;
            }

            return base.OrdinaryHasInstance(v);
        }

        public override bool DefineOwnProperty(JsValue property, PropertyDescriptor desc)
        {
            return false;
        }

        public override bool Delete(JsValue property)
        {
            return false;
        }

        public override bool Set(JsValue property, JsValue value, JsValue receiver)
        {
            if (!CanPut(property))
            {
                return false;
            }

            var ownDesc = GetOwnProperty(property);
            ownDesc.Value = value;
            return true;
        }

        public override PropertyDescriptor GetOwnProperty(JsValue property)
        {
            if (property is not JsString jsString)
            {
                if (property == GlobalSymbolRegistry.HasInstance)
                {
                    var hasInstanceFunction = new ClrFunctionInstance(
                        Engine,
                        "[Symbol.hasInstance]",
                        HasInstance,
                        1,
                        PropertyFlag.Configurable);

                    var hasInstanceProperty = new PropertyDescriptor(hasInstanceFunction, PropertyFlag.AllForbidden);
                    SetProperty(GlobalSymbolRegistry.HasInstance, hasInstanceProperty);
                    return hasInstanceProperty;
                }
            }
            else
            {
                var key = jsString._value;

                if (_properties?.TryGetValue(key, out var descriptor) != true)
                {
                    descriptor = CreatePropertyDescriptor(key);
                    if (!ReferenceEquals(descriptor, PropertyDescriptor.Undefined))
                    {
                        _properties ??= new PropertyDictionary();
                        _properties[key] = descriptor;
                        return descriptor;
                    }
                }
            }

            return base.GetOwnProperty(property);
        }

        private PropertyDescriptor CreatePropertyDescriptor(string name)
        {
            var key = new MemberAccessorKey(ReferenceType, name);
            var accessor = _memberAccessors.GetOrAdd(key, x => ResolveMemberAccessor(_engine, x.Type, x.PropertyName));
            return accessor.CreatePropertyDescriptor(_engine, ReferenceType, enumerable: true);
        }

        private static ReflectionAccessor ResolveMemberAccessor(Engine engine, Type type, string name)
        {
            var typeResolver = engine.Options.Interop.TypeResolver;

            if (type.IsEnum)
            {
                var memberNameComparer = typeResolver.MemberNameComparer;
                var typeResolverMemberNameCreator = typeResolver.MemberNameCreator;

                var enumValues = Enum.GetValues(type);
                var enumNames = Enum.GetNames(type);

                for (var i = 0; i < enumValues.Length; i++)
                {
                    var enumOriginalName = enumNames.GetValue(i)?.ToString() ?? "";
                    var member = type.GetMember(enumOriginalName)[0];
                    foreach (var exposedName in typeResolverMemberNameCreator(member))
                    {
                        if (memberNameComparer.Equals(name, exposedName))
                        {
                            var value = enumValues.GetValue(i)!;
                            return new ConstantValueAccessor(JsNumber.Create(value));
                        }
                    }
                }

                return ConstantValueAccessor.NullAccessor;
            }

            const BindingFlags BindingFlags = BindingFlags.Public | BindingFlags.Static | BindingFlags.FlattenHierarchy;
            return typeResolver.TryFindMemberAccessor(engine, type, name, BindingFlags, indexerToTry: null, out var accessor)
                ? accessor
                : ConstantValueAccessor.NullAccessor;
        }

        public object Target => ReferenceType;

        private static JsValue HasInstance(JsValue thisObject, JsValue[] arguments)
        {
            var typeReference = thisObject as TypeReference;
            var other = arguments.At(0);

            if (typeReference is null)
            {
                return JsBoolean.False;
            }

            var baseType = typeReference.ReferenceType;

            var derivedType = other switch
            {
                ObjectWrapper wrapper => wrapper.Target.GetType(),
                TypeReferencePrototype otherTypeReference => otherTypeReference.TypeReference.ReferenceType,
                _ => null
            };

            return derivedType != null && baseType != null && (derivedType == baseType || derivedType.IsSubclassOf(baseType));
        }

        public override string ToString()
        {
            return "[CLR type: " + ReferenceType + "]";
        }
    }
}
